Research in the McClure lab is focused on understanding how pollen pistil communication controls plant mating. We study S-RNase-based self-incompatibility in Nicotiana and interspecific pollen recognition and rejection between tomato and its wild relatives. The genus Nicotiana is useful because of its ease of experimental manipulation, and the inter- and intra-specific compatibility relationships are well known. For example, N. alata displays gametophytic self-incompatibility (SI). Self-pollen and pollen from closely related plants are rejected, thus maintaining hybrid vigor. N. alata also has specific mechanisms for recognizing and rejecting pollen from related species, such as N. plumbaginifolia and N. tabacum. Likewise, tomato, Solanum lycopersicum (formerly Lycopersicon esculentum), also has well-defined crossing relationships with its wild relatives such as SI S. habrochaities and SI S. pennellii. In addition, there are many powerful genetic tools available for studies of tomato.

We use genetic and biochemical techniques to identify factors that contribute to inter- and intra-specific pollen recognition and rejection. A theme for pollen-pistil interactions is that the pistil secretes factors into the extracellular matrix that pollen tubes use as a guide to the ovary. Our challenge is to identify these factors, and the pollen factors they interact with, to control mating. In SI, for example, the pistil produces potentially cytotoxic proteins, called S-RNases, that are taken up by growing pollen tubes. When pollen is rejected, S-RNase is released into the pollen tube cytoplasm, and growth is inhibited. Thus, our research involves biochemical and genetic experiments to identify critical pollen and pistil proteins and cell biological experiments to determine how their cellular context contributes to their functions. By understanding the natural systems that control pollination, plant breeders can design new strategies to control plant breeding behavior to their own purposes.